Math lesson plan · 7th grade (Year 8 in England) · 45 minutes
Use decimal multipliers for percentage change
Decimals and percentages
CCSS 7.RP.A.3CCSS 7.EE.A.2England: KS3 NumberEngland: GCSE Foundation Ratio
Objective and success criteria
Students will: Use decimal multipliers for percentage change.
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Increase an amount by a percentage; Decrease an amount by a percentage
Leads to: the next skill in this area.
Materials: Place value chart with tenths and hundredths, Hundred squares, Number lines, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 5 min
- Quick retrieval from earlier learning (Increase an amount by a percentage; Decrease an amount by a percentage). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Increase 780 by 20%. → 936Prompt: Find 20% of 780.
- Decrease 300 by 40%. → 180Prompt: Find 40% of 300.
- A video had 2100 views. Views went up by 35% the next day. How many views did it have then? → 2835Prompt: Increasing by 35% means you end up with 135%.
Hook · 5 min
- Show two prices or race times with decimals and ask which is bigger, then why.
- Share the objective: Use decimal multipliers for percentage change. Read the success criteria together.
I do: model it · 10 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: What single number do you multiply by to increase an amount by 12%?
- Step 1: 112% = 1.12
- Answer: 1.12
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 10 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- What single number do you multiply by to increase an amount by 40%? → 1.4Prompt: The original amount is 100%. After the change you have 140%.
- An amount is multiplied by 0.92. What percentage change is that? (Decrease of 92% / Increase of 8% / Decrease of 8% / Increase of 0.92%) → Decrease of 8%Prompt: Multiplying by 1 means no change.
You do: independent practice · 10 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 5 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- What single number do you multiply by to decrease an amount by 17.5%? → 0.825Prompt: The original amount is 100%. After the change you have 82.5%.
- Use a multiplier to decrease 1050 by 22%. → 819Prompt: The multiplier is 1 − 0.22.
Watch out for
- Thinking 0.45 is bigger than 0.5 because 45 is bigger than 5.
- Moving the digits the wrong way when multiplying or dividing by 10.
Support and stretch
Support
- Review first: Increase an amount by a percentage.
- Use concrete materials: place value chart with tenths and hundredths.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/math/grade-7.
Free lesson plan from eurekami.com/lesson-plan-builder